GoodStones.cpp

class Solution{
public:
    int goodStones(int n,vector<int> &arr){
        // Code here
        vector<int>dp(n,0);
        for(int i=0;i<n;i++){
            if(dp[i]==0){
                int temp=i;
                bool good =false;
                while(dp[temp]!=1){
                    if(arr[temp]==0)break;
                    //mark visited
                    dp[temp]=1;
                    //next index
                    temp+=arr[temp];
                    if(temp<0 || temp>=n || dp[temp]==2){
                        good =true;
                        break;
                    }
                }
                if(good){
                    temp=i;
                    while(temp>=0 && temp<n){
                        dp[temp]=2;
                        temp+=arr[temp];
                    }
                }
            }
        }
        int ans=0;
        for(int i=0;i<n;i++){
            if(dp[i]==2)ans++;
        }
        return ans;
    }  
};